1. Field of the Invention
The present invention relates to a method of washing dishes by which food such as the remains of a meal is prevented from sticking to dish surfaces, and further relates to apparatus, sticking inhibitors and rinsing assistants used for the method.
2. Description of the Prior Art
There is conventionally provided such a dishwasher as shown in FIG. 27, as a dishwasher for business use, for example, in restaurants. This business-use dishwasher is arranged in the following way: A rack 27 on which dishes B are placed is accommodated between pairs of washing arms 23, 24 and rinsing arms 25, 26, each pair being oppositely disposed above and below in a washing chamber 22 provided in a casing 21 and the pairs being adapted to spin. A detergent C stored at the bottom of the washing chamber 22 is sprayed from the washing arms 23, 24 through washing piping 30 by a washing pump 29 having a filter 28, thereby washing dishes. After that, tap water passing through an electromagnetic valve 31 is warmed by an electric water heater 32, and the resulting warm water W is sprayed from the rinsing arms 25, 26 through rinsing piping 33 so as to rinse the dishes B. In addition, detergent and water are discharged outside from a drain 35 through drain piping 36 before overflowing a strainer pan 34 located at the bottom of the washing chamber 22.
The dishes B, washed with the detergent rinsed with the warm water, are allowed to dry by themselves without the need of toweling by virtue of a high temperature of the above-mentioned warm water as much as 80.degree. C. or so, and drawn out of the washing chamber 22 after drying.
On the other hand, a conventional dishwasher for household use is shown in FIG. 28. This household-use dishwasher is arranged in the following way: A rack 73 on which dishes B are placed is accommodated in a washing chamber 72 provided in a casing 71. A detergent C stored in a reservoir 74 at the bottom of the washing chamber 72 is sprayed up toward the rack 73 from an arm 78 through piping 77 by a circulating pump 76 having a filter 75. After washing dishes B, the detergent C in the reservoir 74 is drained by a drain pump 79. Then an electromagnetic valve 80 is opened so that the reservoir 74 is filled with fresh water to the brim through a water supply pipe 81. The supplied fresh water is resprayed from the arm 78 by the circulating pump 76, thereby rendering the rinsing of the dishes B at least one time. The dishes B washed with the detergent and rinsed with the fresh water are taken out of the washing chamber 72 and toweled.
Thus, the dishes B after the washing and drying through the business-use and household-use dishwashers are filled with food such as rice or meat and vegetables, and served to customers in a restaurant or members of a family.
In the rinsing process, in either case of the above-mentioned dishwashers, a rinsing assistant based on a surface-active agent is added to the warm water W or fresh water. This rinsing assistant serves to accelerate the wetting of dish surfaces and to cause film-like flow of water to take place on dish surfaces, thereby washing away the detergent having been used in the washing process and remaining on dish surfaces. The rinsing assistant also prevents concentration of insoluble matters such as mineral matters contained in the water from occurring on dish surfaces as water spots, when the dishes are heated by warm water in a washing process or rinsing process, and the film-like water on the surface of the dishes is evaporated by the remaining heat of the dishes.
When rice served to customers in a restaurant is uneaten and left on dish surfaces, the rice becomes increasingly dried as time goes on, sticking to dish surfaces still more fixedly. There arises a problem therefrom that only washing the dishes with a business-use dishwasher will not readily remove the remains of rice. This problem, in particular, will be more serious and critical in business-use dishwashers that are designed to wash a bulk of dishes having been left for a long time period after use, unlike in household-use dishwashers.
As a result, to solve the above problem, restaurants or the like have conventionally adopted such a countermeasure that after-use dishes to which the remains of rice are sticking are immersed in a bath before washing so as to make them easily removed. This countermeasure, however, takes substantial time and labor for the immersion, which would be an obstacle to saving time and labor in dish washing as originally intended for the dishwashers.
Further, in households, it is often the case that all members of a family cannot take a meal together and therefore dishes of the first person that has taken a meal are washed together with those of the last person that has taken a meal. In small-in-number families, as another case, dishes for a meal and dishes for the successive meal may collectively be washed. In such cases, the remains of rice are sticking to dishes fixedly at the time of washing, with the result that the remains will not be removed unless the dishes are washed by a household-use dishwasher for a long time.
As the above-mentioned rinsing assistant used in the rinsing process, examples include a surfactant of an ester formed of a polyhydroxy alcohol such as sorbitan (trade name) or sucrose and a fatty acid such as capric acid or stearic acid, or a surfactant based on the partial ester thereof or one of a Pulronic-series (trade name). Disadvantageously, these rinsing assistants have a defect that the surfactant itself remains on dish surfaces as stains or water spots, or decreases the gloss of dish surfaces. Moreover, the above-mentioned rinsing assistants in all cases can be used only in a narrow concentration range of 100 to 50 ppm, making the concentration preparation thereof difficult.